This invention relates to manhole sealing systems and, in particular, to an apparatus and method for molding a sealing material to establish a fluid-tight seal and bond either between a manhole and a manhole frame supported on the manhole or between two sections of a manhole. More particularly, this invention relates to an apparatus and method for providing a mold that can be filled with sealing material to establish a seal to block unwanted inflow of groundwater through a space between the manhole and manhole frame or between two sections of a manhole.
A manhole is a large diameter vertical pipe often made of brick or a series of precast concrete sections that extends downward from a point just below street level to a buried sewer pipe included in a municipal sewerage system. Typically, a heavy cast iron manhole frame is placed on the circular top edge of the manhole to hold a manhole cover above the top end of the manhole at street level. While the manhole cover is visible to someone standing on the street, the manhole frame supporting the cover usually is hidden from view.
In some cases, the street or sidewalk pavement around the manhole frame acts to hold the manhole frame in place on the manhole. It is also known to use bolts or other hardware to anchor the manhole frame to the underlying manhole. The familiar manhole cover rests on a circular ledge provided near the top end of the manhole frame to lie at street level. Removal of the manhole cover from the frame exposes a vertical access aperture that extends downwardly through the hollow manhole frame to enable service workers to pass through the manhole frame to reach the downwardly extending manway passage provided inside the manhole.
Most municipalities are provided with two types of sewerage systems. The first type is a sewage disposal sewer system, which is designed to carry off refuse fluids and waste products to a sewage treatment plant. The second type, often referred to as a "storm sewer" system, is connected to street drains and the like to carry off surface water. A serious problem arises when rainwater or groundwater leaks into a manhole connected to the sewage disposal sewer system. The typical sewage treatment plant provided to process sewage conducted through a sewage disposal system is designed to handle sewage only and is not designed to have enough capacity to handle large volumes of surface water that leak into the sewage disposal sewers through leaky manholes.
A small gap between the top face of the manhole and the bottom face of the manhole frame (or at the joint between two abutting manhole sections) can provide just enough space for significant amounts of rainwater, groundwater, or other liquids to leak from the surrounding ground into the manhole and the sewage disposal sewer pipes connected to the manhole. The capacity of a sewerage system having a sizable number of leaky manhole frames can be overloaded quite easily during prolonged and heavy rainstorms.
A gap between a manhole frame and an underlying manhole large enough to permit surface water to leak into a manhole can develop in several different ways. Manhole frames tend to vibrate due to loads applied by traffic moving on the street and over the manhole cover and, over time, such vibration can cause even heavy manhole frames to move off the underlying manhole to form a gap therebetween. Such movement can occur even though the manhole frame is initially anchored in some way to the manhole. Thermal contraction or expansion of manhole components might also cause the components to shift relative to one another, creating a gap. Likewise, ground movement resulting from freezing and thawing or earth consolidation may create a gap. Also, any seal established between the manhole and manhole frame can deteriorate or fail over time and cause a leakage gap to develop.
A leakage gap can also develop at the joint between two abutting manhole cylinders. Manholes are typically formed by connecting precast concrete cylinders together in series to establish a long manhole unit. Water inflow problems can arise if any gaps develop at the joint between a pair of adjoining cylinders. Here again, poor anchoring and sealing connection problems may cause gaps to develop. It is also common for leaks to develop because one manhole cylinder has moved relative to an adjoining manhole cylinder or because a seal provided between the two cylinders has failed.
Attempts have been made to provide various types of devices to prevent manhole leakage problems. For example, U.S. Pat. No. 4,557,625 to Jahnke et al. Another manhole sealing device is described in U.S. Pat. No. 4,582,449 to Vosswinkel.
An apparatus and method for molding a sealing material to establish a fluid-tight sealing bond closing any gap between an inground manhole and a manhole frame without removing the manhole frame from its mounted position on the manhole would simplify rehabilitation of leaky manholes. An apparatus and method that could also be used to fill and close any gap at the joint between abutting manhole cylinder portions would also provide many benefits to manhole installation and rehabilitation work crews. Also, an apparatus and method that could be applied to solve fluid inflow problems affecting a great number of manholes in a sewerage network quickly, simply, and at low cost would be welcomed by many managers of city and metropolitan sewerage systems.
According to the present invention, a mold apparatus is provided for use in a manhole assembly to seal a joint between two abutting manhole components. The mold apparatus includes an open ring, a retaining band coupling the ring to one of the manhole components so that the ring forms a ring-shaped channel at the joint, and a sealant dispenser for conveying sealing material into the channel. The sealing material hardens in the ring-shaped channel and forms a bond at the joint between the two abutting manhole components.
The open ring includes an upper annular portion, a lower annular portion spaced apart radially outwardly from the upper annular portion, and an intermediate portion extending radially between the upper annular portion and the lower annular portion. The retaining band engages the lower annular portion to urge the lower annular portion into engagement with the second manhole component and to place the upper annular portion in spaced-apart confronting relationship with the joint. When the retaining band positions the open ring in the manhole in this manner, the intermediate portion and the upper annular portion of the open ring cooperate to define an annular channel at the joint.
In preferred embodiments, the lower annular portion includes a radially outwardly directed face and a radially inwardly directed face. A strip of adhesive is positioned on the radially outwardly directed face for contact with the interior wall of one of the manhole components.
If the first manhole component is a manhole frame, and the second manhole component is a manhole, the mold apparatus is positioned to straddle the joint between the manhole frame and the manhole to prevent unwanted inflow of fluids in any gaps which may have formed at the joint. A radially outwardly directed face of the lower annular portion of the open ring is positioned to engage the cylindrical interior side wall of the manhole. This brings the upper annular portion and the intermediate portion into proper position to establish the ring-shaped channel at the joint.
Alternatively, if the first manhole component is a first manhole section and the second manhole component is a second manhole section abutting the first manhole section, the mold apparatus is positioned to straddle the joint between the first and second manhole sections to prevent leakage at that joint. A radially outwardly directed face of the bottom annular portion of the open ring is positioned to engage the cylindrical interior wall of the second manhole section. This brings the upper annular portion and the intermediate portion into position to establish the ring-shaped channel at the joint.
The present invention also provides a method of providing a sealed bond at a joint between two abutting manhole components. The method includes the steps of positioning a mold apparatus in proximity to the joint, coupling the mold apparatus to one of the manhole components to form a ring-shaped channel at the joint, filling the ring-shaped channel with a sealing material, and curing the sealing material to create the sealed bond at the joint to block leakage of fluids between the two manhole components.
The present invention further provides a kit having component parts for use in sealing a joint between two abutting manhole components. The kit includes the combination of a plurality of open rings of differing diameters, a plurality of open annular retaining bands sized to engage the plurality of open rings, and a supply of sealing material. The kit may also include a mixing paddle for mixing the components of the sealing material to form a sealant mixture and a supply of primer suitable for application to the open rings to prepare surfaces of the open rings for contact with the sealing material.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.